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嵌入式https://blog.csdn.net/weixin_45791458/category_12768532.html?spm1001.2014.3001.5482 启动文件(Startup File)是嵌入式系统开发中的核心组件之一#xff0c;它用于初始化系统并为主程序的运行做好准备。在大多数情况下#xff0c;启动文件是用汇编语言编…相关阅读
嵌入式https://blog.csdn.net/weixin_45791458/category_12768532.html?spm1001.2014.3001.5482 启动文件(Startup File)是嵌入式系统开发中的核心组件之一它用于初始化系统并为主程序的运行做好准备。在大多数情况下启动文件是用汇编语言编写的并且与具体的处理器架构和工具链紧密相关。本文将以startup_stm32f103xe.s文件为例说明启动文件中做了什么。
1、文件说明
;******************** (C) COPYRIGHT 2017 STMicroelectronics ********************
;* File Name : startup_stm32f103xe.s
;* Author : MCD Application Team
;* Description : STM32F103xE Devices vector table for MDK-ARM toolchain.
;* This module performs:
;* - Set the initial SP
;* - Set the initial PC Reset_Handler
;* - Set the vector table entries with the exceptions ISR address
;* - Configure the clock system
;* - Branches to __main in the C library (which eventually
;* calls main()).
;* After Reset the Cortex-M3 processor is in Thread mode,
;* priority is Privileged, and the Stack is set to Main.
;******************************************************************************
;* attention
;*
;* Copyright (c) 2017 STMicroelectronics.
;* All rights reserved.
;*
;* This software component is licensed by ST under BSD 3-Clause license,
;* the License; You may not use this file except in compliance with the
;* License. You may obtain a copy of the License at:
;* opensource.org/licenses/BSD-3-Clause
;*
;****************************************************************************** 根据注释说明该启动文件用于MDK-ARM工具链完成以下任务
设置初始堆栈指针(SP)。设置初始程序计数器(PC)指向Reset_Handler。初始化向量表指定中断和异常处理函数的入口地址。配置系统时钟。跳转到 C 库的__main最终调用用户定义的main()。 在复位后Cortex-M3处理器处于线程模式(Thread Mode)、特权级(Privileged)使用主堆栈(Main Stack)。 2、栈开辟
; Amount of memory (in bytes) allocated for Stack
; Tailor this value to your application needs
; h Stack Configuration
; o Stack Size (in Bytes) 0x0-0xFFFFFFFF:8
; /hStack_Size EQU 0x00000400AREA STACK, NOINIT, READWRITE, ALIGN3
Stack_Mem SPACE Stack_Size
__initial_sp 首先定义了一个名为Stack_Size的常量1024它表示栈的大小根据上方的Configuration提示栈大小按照8字节对齐。 随后定义了一块名为STACK的内存区域该区域不需要初始化可读可写且起始地址按照2^38字节对齐。 接着定义了一个名为Stack_Mem的内存块其大小为Stack_Size即1024。 最后定义标号__initial_sp代表栈的顶部栈是从高地址向低地址生长的该标号表示的地址也是堆栈寄存器(SP)的初始值。 3、堆开辟
; h Heap Configuration
; o Heap Size (in Bytes) 0x0-0xFFFFFFFF:8
; /hHeap_Size EQU 0x00000200AREA HEAP, NOINIT, READWRITE, ALIGN3
__heap_base
Heap_Mem SPACE Heap_Size
__heap_limit 首先定义了一个名为Heap_Size的常量512它表示堆的大小根据上方的Configuration提示堆大小按照8字节对齐。 随后定义了一块名为HEAP的内存区域该区域不需要初始化可读可写且起始地址按照2^38字节对齐。 接着定义标号__heap_base表示堆的起始地址。 然后定义了一个名为Heap_Mem的内存块其大小为Heap_Size即512。 最后定义标号__heap_limit表示堆的结束地址。 4、指针对齐和指令集说明 PRESERVE8THUMB PRESERVE8设置了PRES8构建属性表示栈指针(SP)保持8字节对齐。THUMB表示接下来的指令是THUMB指令。 5、向量表定义
; Vector Table Mapped to Address 0 at ResetAREA RESET, DATA, READONLYEXPORT __VectorsEXPORT __Vectors_EndEXPORT __Vectors_Size__Vectors DCD __initial_sp ; Top of StackDCD Reset_Handler ; Reset HandlerDCD NMI_Handler ; NMI HandlerDCD HardFault_Handler ; Hard Fault HandlerDCD MemManage_Handler ; MPU Fault HandlerDCD BusFault_Handler ; Bus Fault HandlerDCD UsageFault_Handler ; Usage Fault HandlerDCD 0 ; ReservedDCD 0 ; ReservedDCD 0 ; ReservedDCD 0 ; ReservedDCD SVC_Handler ; SVCall HandlerDCD DebugMon_Handler ; Debug Monitor HandlerDCD 0 ; ReservedDCD PendSV_Handler ; PendSV HandlerDCD SysTick_Handler ; SysTick Handler; External InterruptsDCD WWDG_IRQHandler ; Window WatchdogDCD PVD_IRQHandler ; PVD through EXTI Line detectDCD TAMPER_IRQHandler ; TamperDCD RTC_IRQHandler ; RTCDCD FLASH_IRQHandler ; FlashDCD RCC_IRQHandler ; RCCDCD EXTI0_IRQHandler ; EXTI Line 0DCD EXTI1_IRQHandler ; EXTI Line 1DCD EXTI2_IRQHandler ; EXTI Line 2DCD EXTI3_IRQHandler ; EXTI Line 3DCD EXTI4_IRQHandler ; EXTI Line 4DCD DMA1_Channel1_IRQHandler ; DMA1 Channel 1DCD DMA1_Channel2_IRQHandler ; DMA1 Channel 2DCD DMA1_Channel3_IRQHandler ; DMA1 Channel 3DCD DMA1_Channel4_IRQHandler ; DMA1 Channel 4DCD DMA1_Channel5_IRQHandler ; DMA1 Channel 5DCD DMA1_Channel6_IRQHandler ; DMA1 Channel 6DCD DMA1_Channel7_IRQHandler ; DMA1 Channel 7DCD ADC1_2_IRQHandler ; ADC1 ADC2DCD USB_HP_CAN1_TX_IRQHandler ; USB High Priority or CAN1 TXDCD USB_LP_CAN1_RX0_IRQHandler ; USB Low Priority or CAN1 RX0DCD CAN1_RX1_IRQHandler ; CAN1 RX1DCD CAN1_SCE_IRQHandler ; CAN1 SCEDCD EXTI9_5_IRQHandler ; EXTI Line 9..5DCD TIM1_BRK_IRQHandler ; TIM1 BreakDCD TIM1_UP_IRQHandler ; TIM1 UpdateDCD TIM1_TRG_COM_IRQHandler ; TIM1 Trigger and CommutationDCD TIM1_CC_IRQHandler ; TIM1 Capture CompareDCD TIM2_IRQHandler ; TIM2DCD TIM3_IRQHandler ; TIM3DCD TIM4_IRQHandler ; TIM4DCD I2C1_EV_IRQHandler ; I2C1 EventDCD I2C1_ER_IRQHandler ; I2C1 ErrorDCD I2C2_EV_IRQHandler ; I2C2 EventDCD I2C2_ER_IRQHandler ; I2C2 ErrorDCD SPI1_IRQHandler ; SPI1DCD SPI2_IRQHandler ; SPI2DCD USART1_IRQHandler ; USART1DCD USART2_IRQHandler ; USART2DCD USART3_IRQHandler ; USART3DCD EXTI15_10_IRQHandler ; EXTI Line 15..10DCD RTC_Alarm_IRQHandler ; RTC Alarm through EXTI LineDCD USBWakeUp_IRQHandler ; USB Wakeup from suspendDCD TIM8_BRK_IRQHandler ; TIM8 BreakDCD TIM8_UP_IRQHandler ; TIM8 UpdateDCD TIM8_TRG_COM_IRQHandler ; TIM8 Trigger and CommutationDCD TIM8_CC_IRQHandler ; TIM8 Capture CompareDCD ADC3_IRQHandler ; ADC3DCD FSMC_IRQHandler ; FSMCDCD SDIO_IRQHandler ; SDIODCD TIM5_IRQHandler ; TIM5DCD SPI3_IRQHandler ; SPI3DCD UART4_IRQHandler ; UART4DCD UART5_IRQHandler ; UART5DCD TIM6_IRQHandler ; TIM6DCD TIM7_IRQHandler ; TIM7DCD DMA2_Channel1_IRQHandler ; DMA2 Channel1DCD DMA2_Channel2_IRQHandler ; DMA2 Channel2DCD DMA2_Channel3_IRQHandler ; DMA2 Channel3DCD DMA2_Channel4_5_IRQHandler ; DMA2 Channel4 Channel5
__Vectors_End__Vectors_Size EQU __Vectors_End - __Vectors 首先定义了一块名为RESET的内存区域该区域存储数据且是只读的。 随后导出了三个标号__Vectors、__Vectors_End和__Vectors_Size以便其他文件中引用它们。 从标号__Vectors开始使用DCD指令定义了多个中断函数的地址包括系统内核中断和外部中断两类可以看出最低地址存放着栈顶的初始化地址即__initial_sp。最后用__Vectors_End标号表示向量表的结束并计算出标号__Vectors_Size的值。 6、定义默认中断函数 AREA |.text|, CODE, READONLY; Reset handler
Reset_Handler PROCEXPORT Reset_Handler [WEAK]IMPORT __mainIMPORT SystemInitLDR R0, SystemInitBLX R0 LDR R0, __mainBX R0ENDP; Dummy Exception Handlers (infinite loops which can be modified)NMI_Handler PROCEXPORT NMI_Handler [WEAK]B .ENDP
HardFault_Handler\PROCEXPORT HardFault_Handler [WEAK]B .ENDP
MemManage_Handler\PROCEXPORT MemManage_Handler [WEAK]B .ENDP
BusFault_Handler\PROCEXPORT BusFault_Handler [WEAK]B .ENDP
UsageFault_Handler\PROCEXPORT UsageFault_Handler [WEAK]B .ENDP
SVC_Handler PROCEXPORT SVC_Handler [WEAK]B .ENDP
DebugMon_Handler\PROCEXPORT DebugMon_Handler [WEAK]B .ENDP
PendSV_Handler PROCEXPORT PendSV_Handler [WEAK]B .ENDP
SysTick_Handler PROCEXPORT SysTick_Handler [WEAK]B .ENDPDefault_Handler PROCEXPORT WWDG_IRQHandler [WEAK]EXPORT PVD_IRQHandler [WEAK]EXPORT TAMPER_IRQHandler [WEAK]EXPORT RTC_IRQHandler [WEAK]EXPORT FLASH_IRQHandler [WEAK]EXPORT RCC_IRQHandler [WEAK]EXPORT EXTI0_IRQHandler [WEAK]EXPORT EXTI1_IRQHandler [WEAK]EXPORT EXTI2_IRQHandler [WEAK]EXPORT EXTI3_IRQHandler [WEAK]EXPORT EXTI4_IRQHandler [WEAK]EXPORT DMA1_Channel1_IRQHandler [WEAK]EXPORT DMA1_Channel2_IRQHandler [WEAK]EXPORT DMA1_Channel3_IRQHandler [WEAK]EXPORT DMA1_Channel4_IRQHandler [WEAK]EXPORT DMA1_Channel5_IRQHandler [WEAK]EXPORT DMA1_Channel6_IRQHandler [WEAK]EXPORT DMA1_Channel7_IRQHandler [WEAK]EXPORT ADC1_2_IRQHandler [WEAK]EXPORT USB_HP_CAN1_TX_IRQHandler [WEAK]EXPORT USB_LP_CAN1_RX0_IRQHandler [WEAK]EXPORT CAN1_RX1_IRQHandler [WEAK]EXPORT CAN1_SCE_IRQHandler [WEAK]EXPORT EXTI9_5_IRQHandler [WEAK]EXPORT TIM1_BRK_IRQHandler [WEAK]EXPORT TIM1_UP_IRQHandler [WEAK]EXPORT TIM1_TRG_COM_IRQHandler [WEAK]EXPORT TIM1_CC_IRQHandler [WEAK]EXPORT TIM2_IRQHandler [WEAK]EXPORT TIM3_IRQHandler [WEAK]EXPORT TIM4_IRQHandler [WEAK]EXPORT I2C1_EV_IRQHandler [WEAK]EXPORT I2C1_ER_IRQHandler [WEAK]EXPORT I2C2_EV_IRQHandler [WEAK]EXPORT I2C2_ER_IRQHandler [WEAK]EXPORT SPI1_IRQHandler [WEAK]EXPORT SPI2_IRQHandler [WEAK]EXPORT USART1_IRQHandler [WEAK]EXPORT USART2_IRQHandler [WEAK]EXPORT USART3_IRQHandler [WEAK]EXPORT EXTI15_10_IRQHandler [WEAK]EXPORT RTC_Alarm_IRQHandler [WEAK]EXPORT USBWakeUp_IRQHandler [WEAK]EXPORT TIM8_BRK_IRQHandler [WEAK]EXPORT TIM8_UP_IRQHandler [WEAK]EXPORT TIM8_TRG_COM_IRQHandler [WEAK]EXPORT TIM8_CC_IRQHandler [WEAK]EXPORT ADC3_IRQHandler [WEAK]EXPORT FSMC_IRQHandler [WEAK]EXPORT SDIO_IRQHandler [WEAK]EXPORT TIM5_IRQHandler [WEAK]EXPORT SPI3_IRQHandler [WEAK]EXPORT UART4_IRQHandler [WEAK]EXPORT UART5_IRQHandler [WEAK]EXPORT TIM6_IRQHandler [WEAK]EXPORT TIM7_IRQHandler [WEAK]EXPORT DMA2_Channel1_IRQHandler [WEAK]EXPORT DMA2_Channel2_IRQHandler [WEAK]EXPORT DMA2_Channel3_IRQHandler [WEAK]EXPORT DMA2_Channel4_5_IRQHandler [WEAK]WWDG_IRQHandler
PVD_IRQHandler
TAMPER_IRQHandler
RTC_IRQHandler
FLASH_IRQHandler
RCC_IRQHandler
EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
DMA1_Channel1_IRQHandler
DMA1_Channel2_IRQHandler
DMA1_Channel3_IRQHandler
DMA1_Channel4_IRQHandler
DMA1_Channel5_IRQHandler
DMA1_Channel6_IRQHandler
DMA1_Channel7_IRQHandler
ADC1_2_IRQHandler
USB_HP_CAN1_TX_IRQHandler
USB_LP_CAN1_RX0_IRQHandler
CAN1_RX1_IRQHandler
CAN1_SCE_IRQHandler
EXTI9_5_IRQHandler
TIM1_BRK_IRQHandler
TIM1_UP_IRQHandler
TIM1_TRG_COM_IRQHandler
TIM1_CC_IRQHandler
TIM2_IRQHandler
TIM3_IRQHandler
TIM4_IRQHandler
I2C1_EV_IRQHandler
I2C1_ER_IRQHandler
I2C2_EV_IRQHandler
I2C2_ER_IRQHandler
SPI1_IRQHandler
SPI2_IRQHandler
USART1_IRQHandler
USART2_IRQHandler
USART3_IRQHandler
EXTI15_10_IRQHandler
RTC_Alarm_IRQHandler
USBWakeUp_IRQHandler
TIM8_BRK_IRQHandler
TIM8_UP_IRQHandler
TIM8_TRG_COM_IRQHandler
TIM8_CC_IRQHandler
ADC3_IRQHandler
FSMC_IRQHandler
SDIO_IRQHandler
TIM5_IRQHandler
SPI3_IRQHandler
UART4_IRQHandler
UART5_IRQHandler
TIM6_IRQHandler
TIM7_IRQHandler
DMA2_Channel1_IRQHandler
DMA2_Channel2_IRQHandler
DMA2_Channel3_IRQHandler
DMA2_Channel4_5_IRQHandlerB .ENDPALIGN 首先定义了一块名为.text的内存区域该区域存储代码且是只读的。
6.1、复位中断函数
; Reset handler
Reset_Handler PROCEXPORT Reset_Handler [WEAK]IMPORT __mainIMPORT SystemInitLDR R0, SystemInitBLX R0 LDR R0, __mainBX R0ENDP 定义了一个名为Reset_Handler的标号PROC表示这是一个过程即函数随后Reset_Handler标号被导出并被标记为弱标号即如果没有在其他地方提供Reset_Handler则会使用这里定义的弱定义。两个IMPORT语句表示__main和SystemInit标号来自于其他文件随后使用LDR和BLX指令配合跳转执行SystemInit函数它是一个系统初始化函数在system_stm32f1xx.c中定义用于配置硬件如时钟、外设等。最后跳转执行__main函数它是一个C库函数它用于初始化程序的各个段和寄存器并最终执行用户定义的main函数。其中BX指令不会保存当前PC即__main函数不会返回。 6.2、其他系统内核中断函数
; Dummy Exception Handlers (infinite loops which can be modified)NMI_Handler PROCEXPORT NMI_Handler [WEAK]B .ENDP
HardFault_Handler\PROCEXPORT HardFault_Handler [WEAK]B .ENDP
MemManage_Handler\PROCEXPORT MemManage_Handler [WEAK]B .ENDP
BusFault_Handler\PROCEXPORT BusFault_Handler [WEAK]B .ENDP
UsageFault_Handler\PROCEXPORT UsageFault_Handler [WEAK]B .ENDP
SVC_Handler PROCEXPORT SVC_Handler [WEAK]B .ENDP
DebugMon_Handler\PROCEXPORT DebugMon_Handler [WEAK]B .ENDP
PendSV_Handler PROCEXPORT PendSV_Handler [WEAK]B .ENDP
SysTick_Handler PROCEXPORT SysTick_Handler [WEAK]B .ENDP其他的系统内核中断函数的函数定义都是一个无限循环B .开发者需要在其他地方为这些函数提供实际的实现。 6.3、外部中断函数
Default_Handler PROCEXPORT WWDG_IRQHandler [WEAK]EXPORT PVD_IRQHandler [WEAK]EXPORT TAMPER_IRQHandler [WEAK]EXPORT RTC_IRQHandler [WEAK]EXPORT FLASH_IRQHandler [WEAK]EXPORT RCC_IRQHandler [WEAK]EXPORT EXTI0_IRQHandler [WEAK]EXPORT EXTI1_IRQHandler [WEAK]EXPORT EXTI2_IRQHandler [WEAK]EXPORT EXTI3_IRQHandler [WEAK]EXPORT EXTI4_IRQHandler [WEAK]EXPORT DMA1_Channel1_IRQHandler [WEAK]EXPORT DMA1_Channel2_IRQHandler [WEAK]EXPORT DMA1_Channel3_IRQHandler [WEAK]EXPORT DMA1_Channel4_IRQHandler [WEAK]EXPORT DMA1_Channel5_IRQHandler [WEAK]EXPORT DMA1_Channel6_IRQHandler [WEAK]EXPORT DMA1_Channel7_IRQHandler [WEAK]EXPORT ADC1_2_IRQHandler [WEAK]EXPORT USB_HP_CAN1_TX_IRQHandler [WEAK]EXPORT USB_LP_CAN1_RX0_IRQHandler [WEAK]EXPORT CAN1_RX1_IRQHandler [WEAK]EXPORT CAN1_SCE_IRQHandler [WEAK]EXPORT EXTI9_5_IRQHandler [WEAK]EXPORT TIM1_BRK_IRQHandler [WEAK]EXPORT TIM1_UP_IRQHandler [WEAK]EXPORT TIM1_TRG_COM_IRQHandler [WEAK]EXPORT TIM1_CC_IRQHandler [WEAK]EXPORT TIM2_IRQHandler [WEAK]EXPORT TIM3_IRQHandler [WEAK]EXPORT TIM4_IRQHandler [WEAK]EXPORT I2C1_EV_IRQHandler [WEAK]EXPORT I2C1_ER_IRQHandler [WEAK]EXPORT I2C2_EV_IRQHandler [WEAK]EXPORT I2C2_ER_IRQHandler [WEAK]EXPORT SPI1_IRQHandler [WEAK]EXPORT SPI2_IRQHandler [WEAK]EXPORT USART1_IRQHandler [WEAK]EXPORT USART2_IRQHandler [WEAK]EXPORT USART3_IRQHandler [WEAK]EXPORT EXTI15_10_IRQHandler [WEAK]EXPORT RTC_Alarm_IRQHandler [WEAK]EXPORT USBWakeUp_IRQHandler [WEAK]EXPORT TIM8_BRK_IRQHandler [WEAK]EXPORT TIM8_UP_IRQHandler [WEAK]EXPORT TIM8_TRG_COM_IRQHandler [WEAK]EXPORT TIM8_CC_IRQHandler [WEAK]EXPORT ADC3_IRQHandler [WEAK]EXPORT FSMC_IRQHandler [WEAK]EXPORT SDIO_IRQHandler [WEAK]EXPORT TIM5_IRQHandler [WEAK]EXPORT SPI3_IRQHandler [WEAK]EXPORT UART4_IRQHandler [WEAK]EXPORT UART5_IRQHandler [WEAK]EXPORT TIM6_IRQHandler [WEAK]EXPORT TIM7_IRQHandler [WEAK]EXPORT DMA2_Channel1_IRQHandler [WEAK]EXPORT DMA2_Channel2_IRQHandler [WEAK]EXPORT DMA2_Channel3_IRQHandler [WEAK]EXPORT DMA2_Channel4_5_IRQHandler [WEAK]WWDG_IRQHandler
PVD_IRQHandler
TAMPER_IRQHandler
RTC_IRQHandler
FLASH_IRQHandler
RCC_IRQHandler
EXTI0_IRQHandler
EXTI1_IRQHandler
EXTI2_IRQHandler
EXTI3_IRQHandler
EXTI4_IRQHandler
DMA1_Channel1_IRQHandler
DMA1_Channel2_IRQHandler
DMA1_Channel3_IRQHandler
DMA1_Channel4_IRQHandler
DMA1_Channel5_IRQHandler
DMA1_Channel6_IRQHandler
DMA1_Channel7_IRQHandler
ADC1_2_IRQHandler
USB_HP_CAN1_TX_IRQHandler
USB_LP_CAN1_RX0_IRQHandler
CAN1_RX1_IRQHandler
CAN1_SCE_IRQHandler
EXTI9_5_IRQHandler
TIM1_BRK_IRQHandler
TIM1_UP_IRQHandler
TIM1_TRG_COM_IRQHandler
TIM1_CC_IRQHandler
TIM2_IRQHandler
TIM3_IRQHandler
TIM4_IRQHandler
I2C1_EV_IRQHandler
I2C1_ER_IRQHandler
I2C2_EV_IRQHandler
I2C2_ER_IRQHandler
SPI1_IRQHandler
SPI2_IRQHandler
USART1_IRQHandler
USART2_IRQHandler
USART3_IRQHandler
EXTI15_10_IRQHandler
RTC_Alarm_IRQHandler
USBWakeUp_IRQHandler
TIM8_BRK_IRQHandler
TIM8_UP_IRQHandler
TIM8_TRG_COM_IRQHandler
TIM8_CC_IRQHandler
ADC3_IRQHandler
FSMC_IRQHandler
SDIO_IRQHandler
TIM5_IRQHandler
SPI3_IRQHandler
UART4_IRQHandler
UART5_IRQHandler
TIM6_IRQHandler
TIM7_IRQHandler
DMA2_Channel1_IRQHandler
DMA2_Channel2_IRQHandler
DMA2_Channel3_IRQHandler
DMA2_Channel4_5_IRQHandlerB .ENDP 定义了一个名为Default_Handler的标号PROC表示这是一个过程即函数外部中断函数的标号被导出并被标记为弱标号它们表示的地址实际上就是Default_Handler函数的地址如果没有在其他地方对这些外部中断函数进行实现依旧是会进入无限循环B .。 7、堆栈初始化函数 ALIGN;*******************************************************************************
; User Stack and Heap initialization
;*******************************************************************************IF :DEF:__MICROLIBEXPORT __initial_spEXPORT __heap_baseEXPORT __heap_limitELSEIMPORT __use_two_region_memoryEXPORT __user_initial_stackheap__user_initial_stackheapLDR R0, Heap_MemLDR R1, (Stack_Mem Stack_Size)LDR R2, (Heap_Mem Heap_Size)LDR R3, Stack_MemBX LRALIGNENDIFEND ALIGN表示将当前位置对齐到4字节。随后是一段条件编译的代码如果定义了__MICROLIB宏则将标号__initial_sp、__heap_base和__heap_limit导出否则导入__use_two_region_memory标号并导出__user_initial_stackheap标号其中在R0寄存器保存了堆起始地址R1寄存器保存了栈顶地址R2保存了堆结束地址R3保存了栈的地址。最后跳转到标号LR处继续执行且不返回。 定义__MICROLIB可以通过Option选项卡进行如图1所示。 图1 使用微库选项
